Method for automatic depth control for earth moving and grading

ABSTRACT

A method and apparatus for automatically controlling the depth of earth grading for utilization with a grader or paver (30) is disclosed. The method includes determination of time taken for an acoustic pulse to travel from a transducer (10) to a reference surface and back, with this value being used to calibrate a microprocessor-controlled distance-measuring device (100). As the grader moves over a surface to be graded, the distance to the reference surface is constantly detected by a repeated emission and detection of such acoustic pulses. The timing of the echoed pulses is converted to addresses in a look-up table which contains control words symbolizing commands to be given to hydraulic rams carried by the grader. By implementing these commands, the depth of the blade (40) relative to the reference surface is constantly updated, compensating for variations with the height of the reference surface. A thermistor is provided to automatically compensate for temperature variations as the grading takes place. Displays are provided for the operator of the vehicle to show what type of adjustments are being made to the blade, and whether the height of the reference surface is outside the range of sensitivity of the follower. The follower is automatically calibrated for a given blade depth by repeated incrementation of a delay time variable until a zero adjustment command is generated for the blade control.



